GB835834A - Improvements in or relating to electrical generator regulating systems, especially for mechanically propelled vehicles - Google Patents

Abstract

835,834. Automatic voltage control systems. BOSCH G.m.b.H., R. Jan. 14, 1958 [Jan. 19, 1957], No. 1256/58. Addition to 835,210. Class 38 (4). In an automatic voltage control system for a self-excited D.C. generator, in which the field current is controlled by a transistor, in turn controlled by a voltage-sensitive monostable transistor blocking oscillator as in Fig. 13, in the parent Specification; two further forms of load current limiter are provided. As before, and in both embodiments, the base/emitter circuit of a transistor 20 is connected across one diagonal of a voltage sensitive bridge consisting of a rectifier 42 acting as a non-linear resistor and linear resistors 43, 25, 26. The bridge is connected across the output of the generator G, and each time the output voltage rises to cause transistor 20 to conduct, it executes one cycle of oscillation by feed-back from the transformer 21 and applies a negative bias pulse to the base circuit of a transistor 10 controlling the field current. In one embodiment, current limiting is effected by inserting a resistor R between the generator and the load and the voltage measuring circuit (so that as the load current increases the generator voltage rises) and connecting an auxiliary winding 27 on the transformer 21 across the generator in series with a Zener diode 51. Above a limiting value of output current the diode 51 breaks down and the current pulse in winding 27 acts to reduce the generator output. In the second embodiment, Fig. 2 (not shown), the resistor R is included in the base/emitter circuit of the transistor 20 as in the parent Specification, but is shunted by a further resistor and a rectifier acting as a non-liear resistor so as to increase the limiting effect non-linearly as the current increases.